Process for removing non-uniformities in undrawn synthetic filaments



Dec. 5, 1961 DEGREE 0F NONUNIFORHITY H. ALLEY PROCESS FOR REMOVING NON-UNIFORMITIES IN UNDRAWN SYNTHETIC FILAMENTS Filed Jan. 29, 1959 T0 WIND UP 4 6 Iii 45.2

5" 4 6" 8 l2" I6 24" IYD W 2 3 4 5 6 8 l0 I5 ZOYDJNVENTOR HARRY ALLEY BY 0 Q fafl/ ATTORNEY undrawn yarn.

tension required for drawing. --may be carried out as aseparate yarn processing opera- 3,011,215 PROCESS FOR REMOVING NON-UNIFORMITIES IN UNDRAWN SYNTHETIC FILAMENTS Harry Alley, Ayden, N.C., assignor to E. I. du Pont de A Nemours and Company, Wilmington, DeL, a corporation of Delaware Fiied Jan. 29, 1959, Ser. No. 789,920

7 Claims. (Cl. 18-48) This invention is concerned with the preparation of yarns and filaments with improved properties from synthetic linear polymers. More particularly it is concerned with a novel process for improving the uniformity of yarns from synthetic linear polymers.

In the preparation of yarns and filaments from synthetic linear polymers such as the polyamides, e.g., polyhexamethylene adipamide, and the polyesters, e.g., polyethylene terephthalate, it is customary to extrude the molten polymer through a spinneret, cool the filaments thus formed until they have solidified, wind the filaments on a bobbin, and subsequently subject the spun filaments to a drawing operation to enhance their physical properties such as tenacity and elongation.

Although a considerable amount of time and effort has been spent in perfecting this general process and the apparatus required to carry it out, commercial yarns from synthetic polymers still exhibit an objectionable degree of non-uniformity, This non-uniformity may be detected in the yarn, but it is especially apparent in dyed fabrics where the non-uniformity shows up as dye rstreaks.

One source of cyclic non-uniformity which has hitherto defied all efforts at elimination has been found to be associated with the step of winding up the undrawn yarn on the spinning machine. Where the yarn is wound on a bobbin with a fast traverse which forms a flat-faced package, the threadline undergoes a large change in tension at the reversal point of the traverse, and non-uniformities in the yarn have been shown to be associated with these changes in tension. No means has been found for eliminating these cyclic non-uniformities in packaged Going to an entirely different type of yarn winding system would simply give another variety of cyclic variation. Furthermore, the usual drawing processes accentuate these non-uniformities rather than eliminate them.

Therefore, it is an object of this invention to provide a method for removing non-uniformities from undrawn yarns of synthetic linear polymers. A further object is to remove internal tension variations in undrawn yarns from synthetic linear polymers before subjecting them 'to the drawing step. Other objects will be apparent from brieflysubjected ineach stage to a tension below the This tensioning process tion and the undrawn yarn packaged and stored before being subjected to the usual drawing operation, or more advantageously the tensioning process of this invention may be carried out on the drawing machine immediately before supplying yarn to the drawing step and continuous therewith.

The level of tension developed in the yarn in the series of individual tensioning steps of this invention may be 3,011,215 Patented Dec. 5, 1961 "ice constant for the complete series of steps, or the tension level may vary from step to step if so desired. In general,- however, optimum results are obtained when the summation of tension increments for the complete series of tensioning steps, measured in grams, falls between the limits T and T defined by the two equations 1 T1=O.O0718 d+3.0 and (2 T =0.Ol21 d+14.5

where d is the total denier of the (undrawn) yarn bundle being treated. These limits hold for undrawn yarns having deniers in the range from about 60 to about 1500. Multiple tensioning processes in which the summation of tension increments falls appreciably above or below the limits defined by Equations 1 and 2 do not give a noteworthy improvement in yarn uniformity.

The method of applying tension to the yarn is not critical and many different tensioning procedures will be apparent to those skilled in the art. Any one of a number of commercially available tensioning devices may be utilized, it being necessary only that the device be adjustable to give the desired tension level and that a reasonably uniform tension be maintained.

The process of this invention is usually carried out by passing the yarn in a continuous manner over a series the yarn. However, this stressing operation may be carried out in several discrete stages wherein the yarn is packaged and stored between each stressing stage. Where the multiple stressing process is coupled with the drawing process, the forwarding roll of the stressing process may advantageously be the feed roller of the draw machine. 1

The speed of the yarn passing through the stressing operation may be varied within wide limits and in general will depend only upon the ability of the tensioning device to maintain a uniform tension level. Good results have been obtained with speeds as high as 250 y.p.m. and with speeds as low as 25 y.p.m.

The invention is further illustrated in the attached drawings wherein FIGURE 1 is a diagrammatic view of a single tensioning stage, FIGURE 2 is a similar view of a multiple tensioning process, and FIGURE 3 is a spectrographic illustration of the improvement in denier.

uniformity obtainable by the process of this invention.

Referring to FIGURE 1, a single tensioning stage may be carried out by passing the undrawn yarn 2 frorn the supply package 1 through guide 3 to a tensioning device 4, thence to and around a driven roll 5 with its accompanying separator roll 6, and then to a wind-up device or to a subsequent processing step (not shown). To obtain the desired .results the undrawn yarn must pass through at least three such tensioning stages;

FIGURE 2 illustrates an embodiment ofthe invention wherein the undrawn yarn passes through a complete set of tensioning steps without the aid of yarn handling equip ment between tensioning steps. Undrawn yarn 2. is passed from the supply package '1, through guide 3, through multi-fingered tension gate7, through guide 8, around follower roll 9 and then around driven roll 10. Follower roll 9 is a freely rotating weighted roller which presses against driven roll 10 and thereby prevents slippage of the yarn as it passes between the nip of the two rolls. Tension gage 7 possesses two sets of fingers which are urged toward each other by means of weight 11 which is attached by a cord to a leverarm extension of 3 one set of fingers. As the yarn passes between the two sets of fingers of the tension gate it is partially snubbed at each finger because of the friction developed between the yarn and the finger. The number of tensioning stages is equal to the number of fingers contacted by the yarn. The tension level in the yarn between tension gate 7 and roll 9 is adjusted to the desired level by choice of the proper weight 11. Undrawn yarn leaving roll 10 may be wound on a package and subsequently carried through the normal drawing process, or the yarn may proceed directly from roll 10 to the drawing zone. In a preferred embodiment of the invention rolls 9 and 10 may be the feed rolls of the drawing machine.

The multiple-tensioning operation of this invention is not intended to draw the yarn nor to introduce orientation into the yarn. A negligible amount of stretching is accomplished in contrast to the 300-60072: stretch required for true drawing.

Surprisingly, when undrawn yarns from synthetic linear polymers are subjected to the multiple tensioning process of this invention, cyclic non-uniformities are in many cases completely removed and in all cases are markedly reduced in severity. T his improvement in uniformity may be detected by examining the undrawn yarns with the aid of suitable instruments. But more important from the commercial viewpoint, when these yarns are drawn and woven into fabric and then dyed there is a substantial reduction in the occurrence of dyeing streaks normally encountered. There is a particular improvement in those short length cyclic denier variations which show up in certain dyed fabrics as visible patterns.

Cyclic as well as random denier variations in yarn may be detected by apparatus capable of measuring denier continuously along a threadline. One particular apparatus of this type available commercially is the Uster Evenness Tester, Model C, sold by Zellweger Ltd, Uster, Switzerland, which measures variation in denier electronically by means of a capacitance gauge. The varying output, which is a function of denier, is analyzed by the Uster spectrograph which separates cyclic variation from random variation by means of a series of rotating discs in which the frequency of the current is responsive to denier variation. The current from each disc is stored by a condenser; When the recorder circuit is energized, each condenser, a total of 30, is scanned. The recorder trace, called a Uster spectrogram, indicates cyclic denier variation by peaks rising from the base line, and the wave length of the particular cyclic variation is indicated on the top scale of the recorder chart. The height of a peak is an indication of the magnitude of the cyclic defect.

FIGURE 3 is an example of a Uster spectrogram made by the Uster Evenness Tester. The chart shows a trace of a yarn having a cyclic defect at 18 inches and 36 inches. and a trace of a yarn from which these defects have been removed by the process of this invention.

The following examples are cited to illustrate the invention, and are not intended to limit it in any way.

Example I The yarn has a denier of 265 and birefringence of 0.0095.

A test of uniformity using the Uster Evenness Tester, Model C, reveals that the yarn has pronounced cyclic short length non-uniformities which occur at 18 and 36 inch intervals.

This undrawn yarn is subjected to a series of three tensioning operations by passing it three times through the apparatus of FIGURE 1 wherein the tensioning device 4 yarn brake is a General Electric hysteresis brake, Model No. 365E144, adjusted to give a tension of 5.5 grams in the threadline between tensioning device 4 and roll 5. Roll 5 is rotated at a surface speed of 450 y.p.m. The yarn is Wound up on a bobbin after leaving roll 5 of each tensioning operation.

Upon completing the series of tensioning operations the yarn is tested for non-uniformities on the Uster Evenness Tester. In addition to an overall improvement in uniformity the test indicates that the cyclic variations at 18 and 36 inches have been completely eliminated.

Next the undrawn yarn which has been subjected to the multiple tensioning operation is drawn on a drawing machine wherein the yarn is metered by a set of feed rolls to and around a stationary 1.6 inch diameter ceramic pin heated to C. where drawing occurs, passed around a draw roll moving at a surface speed 3.8 times the surface speed of the feed rolls, and then wound up on a yarn take-up device. The drawn yarn is woven into a 36 inch taffeta fabric and then dyed with the dispersed dye Celanthrene Brilliant Blue FPS (CI. 61505). When this fabric is compared with a fabric woven from yarn which did not receive the multiple tensioning operation before drawing, it is found to have remarkably fewer dye streaks and in particular those dye streaks normally associated with cyclic denier defects of the order of 68 and 136 inches which correspond to 18 and 36 inches in the undrawn yarn.

Substantially equivalent results are obtained when the number of tensioning steps is five and the tension applied in each step is 3 grams.

Substantially equivalent results are obtained when the number of tensioning steps is ten and the tension applied in each step is 1.5 grams.

Inferior results are obtained when the number of tensioning steps is two and the tension applied in each step is 8 grams.

Inferior results are obtained when the number'of tensioning steps is three and the tension applied in each step is 1.5 grams.

Substantially equivalent results are obtained when the yarn is spun from a copolymer of polyethylene terephthalate incorporating 2 mol percent of sodium 3,5-di- (carbomethoxy)benzenesulfonate.

Example 11 Polyethylene terephthalate polymer is spun as in Example I to give a 265 denier yarn having a birefringence of 0.0090. Testing indicates that the yarn has the same cyclic short length non-uniformities described for the spun yarn in Example I.

This undrawn yarn is subjected to the tensioning operation outlined schematically in FIGURE 2. The undrawn yarn 2 is passed from the supply package 1 through guide 3, through multi-fingered tension gate 7 (sold commercially by Universal Winding Co, 1954 Catalog Number: 50) which has two sets of 7 ceramic fingers pressing against the yarn from opposite sides, then through guide 8 to and around follower roll 9 and over driven roll 10, and then to a wind-up device. Weight 11 is adjusted to give 12 grams tension in the threadline between gate 7 and guide 8. Roll 10 is rotated at a surface speed of y.p.m.

The undrawn yarn which has been subjected to the multiple tensioning operation described above is then drawn as in Example I. The drawn yarn is woven into a 40 inch satin fabric and dyed with a dispersed dye (CI. 61505). When this fabric is compared with a fabric woven from yarn which did not receive the multiple tensioning operation before drawing, it exhibits a marked reduction in 'streakiness due to non-uniformities in denier.

When both the undrawn and drawn yarn, processed according to this invention, are tested for non-uniformities on the Uster Evenness Tester and compared withyarn which did not receive the multiple tensioning treatment, they are found to be markedly superior in uniformity, with respect to both random non-uniformities and cyclic nonuniformities.

Substantially equivalent results are obtained when the polymer from which the yarn is spun is the polyester of terephthalic acid and trans bis-1,4(hydroxymethyl)cyclohexane.

Substantially equivalent results are obtained when tension gate 7 is adjusted to give threadline tensions, between gate 7 and guide 8, of grams and of 17 grams. In contrast, inferior results are obtained when the threadline tension is 4 grams or 19 grams.

Substantially equivalent results are obtained when the spun yarn bundle consists of 14 filaments instead of 34 filaments, with the same total denier.

Substantially equivalent results are obtained when the yarn is passed through the tensioning process at a speed of 25 y.p.m. or a speed of 250 y.p.m.

Example III 6 exhibit a considerable improvement in appearance due to a decrease in occurrence of dye streaks associated with cyclic denier defects.

Substantially equivalent results are obtained when the yarn is spun from polycaproamide instead of polyhexamethylene adipamide. I 7

Example VI Undrawn polyethylene terephthalate yarn comprised of fifty filaments having a total denier of 950 is tested for uniformity on the Uster Evenness Tester and found ing operation. Rollsj9 and 10 of FIGURE 2 are the feed rolls of the drawing machine and theyarn passes from roll 10 directly to a snubbing pin in the draw zone.

When the drawn yarn is tested for denier non-uniformities along the threadline, the occurrence of cyclic denier defects is found to be substantially eliminated.

The drawn yarn is woven into a 30 inch taffeta fabric and then dyed with a dispersed dye. The fabric is compared with another fabric woven from yarn processed similarly except for the multiple stressing operation prior to drawing and is found to have a considerably improved appearance due to the great reduction in dye streaks associated with cyclic denier defects.

Example IV The polyethylene terephthalate yarn of Example II having a denier of 265, a birefringence of 0.0090, and the same cyclic non-uniformities described in Example I, is subjected to a tensioning operation as outlined in FIG- URE l with the exceptionthat' the single tensioning device 4 is replaced by a series of 4 post-disc snubbing elements (Robert Reiner Inc., Weehawken, N.I.). The weights on the snubbing elements are adjusted to give a tension level of 12 grams between the last snubbing element and driven roll 5. When the product yarn, still undrawn, is checked for uniformity on the Uster Evenness Tester the cyclic denier defects of the original yarn are found to have been substantially eliminated and, in addition, the general level of uniformity is found to be markedly improved. p

Example V 'Polyhexamethylene adipamide having an intrinsic viscosity of 1.0 is melt spun into air through a spinneret having 34 holes and the spun yarn wound up on a bobbin at 1200 y.p.rn. The yarn is found to have a total denier of 315 and a birefringence of 0.0065. A test of uniformity along the threadline using the Uster Evenness Tester reveals that the yarn has pronounced cyclic shortlength non-uniformities as well as an appreciable degree of random non-uniformity.

This undrawn yarn is subjected to the multiple stressing operation of Example II with threadline tension adjusted to 10 grams. When the product yarn is tested for non-uniformities, it is found to be considerably improved over the original spun yarn with respect to random nonuniformity, and cyclic variations have been almost completely eliminated.

The undrawn yarn is then drawn on a drawing machine by passing it from a set of feed rolls to and around a -inch diameter ceramic pin, then around a draw roll rotating with a surface speed 4.5 times that of the surface speed of the feed roll, and then wound up on a yarn take-up device. The product yarn is woven into a 36-inch taffeta fabric and dyed with a dispersed dye as in Example I. When this fabric is compared with a fabric woven from yarn which did not receive the multiple stressing operation prior to drawing,'it is found to Tester and found to be substantially free of cyclic shortlength non-uniformities and to show-a marked reduction in random non-uniformities.

Inferior results are obtained when the tension gate is adjusted to give a threadline tension of 8 grams.

Inferior results are obtained when the tension gate is adjusted to give a threadline tension of 28 grams.

Example VII Undrawn polyethylene terephthalate yarn comprised of 14 filaments and having a total denier of is tested for uniformity on the Uster Evenness Tester and found to exhibit short-length cyclic non-uniformities at 18 and 36 inches in addition to random non-uniformities. This undrawn yarn is subjected to the tensionin-g operation described in Example II with the tension gate adjusted to give a threadline tension of 10 grams. The yarn is then retested on the Uster Evenness Tester and found to be substantially free of cyclic non-uniformit-ies and to show a marked reduction in random non-uniformities.

Inferior results are obtained when the threadline ten sion is maintained at 3 grams.

Inferior results are obtained when the threadline tension is maintained at 18 grams.

While the invention has been illustrated by its application to certain linear polyamides and polyesters, it is to be understood that other similar polyamides and polyesters, as well as their copolymers, may be subjected to the invention with similar advantages.

It is understood that the preceding description is merely intended to be illustrative andthat many variations will be apparent to those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

I claim:

1. The method of removing short-length cyclic nonuniformities in undrawn synthetic linear polymeric filaments which have been wound into a package which comprises subjecting the said filaments to at least three stages of tension without significant drawing.

2. The method of removing short-length cyclic nonuniformities in filaments of synthetic linear polymers which comprises subjecting the undrawn filaments to at least three stages of tension without significant drawing,

" the total tension obtained by the summation of the tensions in each stage measured in grams falls within the limitations of T and T ;'in the equation T =0.00718d+3.0' and T =0.0l21d+14.5

in which d is the total denier of the undrawn filaments being treated.

3. The process of claim 2 in which the filaments are in the form of a yarn bundle having a denier in the range from about 60 to about 1500.

4. The process of claim 2 in which the filaments are made from a linear polyamide.

References Cited in the file of this patent UNITED STATES PATENTS Sykes Jan. .16, 1912 Bradshaw Sept. '3, 1935 Burns Oct, 16, 1951 Furst et a1 July 10, 1956 Shaw Aug. 18, 1959 M ma 

1. THE METHOD OF REMOVING SHORT-LENGTH CYCLIC NONUNIFORMITIES IN UNDRAWN SYNTHETIC LINEAR POLYMERIC FILAMENTS WHICH HAVE BEEN WOUND INTO A PACKAGE WHICH COMPRISES SUBJECTING THE SAID FILAMENTS TO AT LEAST THREE STAGES OF TENSION WITHOUT SIGNIFICANT DRAWING. 